High capacity regenerable graphene-based sorbent
A process of removing a volatile organic compound (VOC) from a gaseous environment, involving contacting a gaseous feedstream containing one or more VOC's, such as an odoriferous compound, an irritant, a contaminant or pollutant, for example, formaldehyde, with a sorbent under conditions sufficient to reduce the concentration of the VOC's in the gaseous feedstream. The sorbent is comprised of a functionalized graphene prepared by amination of graphene oxide. The sorbent is regenerated by adsorbate desorption under mild conditions of air flow. The process can be run through multiple adsorption-desorption cycles in a single fixed bed or swing bed configuration, and is applicable to purifying indoor air and ventilation air as well as reducing pollutants in industrial waste gas streams.
1. A sorbent composition comprising a nitrogen and oxygen-functionalized graphene prepared by a method comprising reacting graphene oxide with an amine of the formula NHR 2 wherein each R is independently selected from the group consisting of hydrogen, C 1-5 alkyl, and C 1-5 aminoalkyl, the reacting occurring in the absence of a carbon nanotube and occurring under process conditions sufficient to prepare the nitrogen and oxygen-functionalized graphene, wherein oxygen is present in the graphene oxide in a concentration greater than 5 percent and less than 40 percent by weight of which carboxyl functionality represents from 30 to 100 percent by weight of the total oxygen.
2. The sorbent composition of claim 1 wherein the amine is aqueous ammonia (ammonium hydroxide).
3. The sorbent composition of claim 1 wherein the amine is reacted with the graphene oxide at a temperature between 50° C. and 120° C. for a time from about 1 hour to about 48 hours.
4. The sorbent composition of claim 1 wherein in the preparation method from greater than 5 percent to essentially 100 percent of oxygen-containing substituents on the graphene oxide are converted to nitrogen-containing substituents.
5. The sorbent composition of claim 1 wherein the nitrogen and oxygen-functionalized graphene has a surface area ranging from about 100 m 2 /g to about 1,000 m 2 /g.
6. The sorbent composition of claim 1 wherein the sorbent is supported on a metal mesh substrate having an ultra-short channel length.
7. The sorbent composition of claim 1 being capable of regeneration at a temperature ranging from 22° C. to 50° C., whereby with each regeneration cycle recovering more than 50 percent of sorbent capacity.
8. An HVAC system comprising the sorbent composition of claim 1 .
9. A stand-alone air purification system comprising the sorbent composition of claim 1 .
10. An industrial sorbent bed comprising the sorbent composition of claim 1 .
11. The sorbent composition of claim 1 , wherein the amine attaches to the functionalized graphene through amide functionalities.
12. The sorbent composition of claim 1 , wherein the graphene oxide is refluxed with the amine and the amine is replenished as needed during reflux.